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Only one core showing a lot of use FIX


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I think I have discovered a bug and a workaround for a common problem.


I noticed after upgrading to 10.5.2 and the ProKit Update that projects that previously played without problems would have several glitches and clicks while playing. Only raising the buffer to 512 from 128 allowed the project to playback normally.


I noted in another thread that I also noticed that only one Core of my Core 2 Duo MBP really seemed to be utilized. It was when this core reached 100% that the glitches would occur. I wouldn't get core overload messages. I guess because the other core wasn't overloaded. But it really wasn't even being used. I have noticed the "one core" thing before 10.5.2, but it seems to have gotten worse.


Here is what I have found out. As it says in the manual when playing in "live" mode, that is when a software synth is in record mode, more CPU is needed. Well it seems since upgrading to 10.5.2 it needs even more. But even more importantly, once a track is put in record mode it seems to take up that much CPU power even when taken out of record mode. Once another track is put into record mode, that track releases the previous track from draining the cpu and it becomes the culprit.


For example: I have a project that has 19 tracks. Each one is a different soft synth. It doesn't seem to matter if they are Logic or 3rd party instruments. If I play it back with track #1 (Piano) in record mode, it will get random CPU spikes and glitches. And the majority of the CPU load for the project will be on one core while the other core shows minimal activity. Take track #1 out of record and the same thing happens. Now mute track #1. No more glitches!


And here it the interesting part: if you then put track #2 in record mode, it will cause the CPU to spike and have glitches. But mute that track and unmute track #1 and again--no more glitches.


I have repeated this in more than one project. And it is consistant.


Here is the workaround: create a "null" softsynth track. Don't insert any plug-ins on the track. And before play back put this track in record mode. Your project will playback with no glitches AND both cores will show similar activity.


If anyone has these same problems and can verify if the above workaround works that would be much appreciated. Thanks!



This is on a MacBook Pro 2.4 Core 2 Duo

4 GB Ram

200GB internal drive


Logic Pro 8.01

Apogee Duet FW interface

(but should be notice that same thing happens when using Built-in)

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Gave your suggestions a shot. No improvement.


Under 10.5.2 a song file is reliably full of stutters and clicks, although it plays to completion. Under 10.4.11 the same song file on the same hardware plays smoothly. Song files are stored on a non-boot drive, and samples are stored on a different non-boot drive. Both systems are using exactly the same resources. Overloads have not been an issue under either OS, nor has HD activity.


These glitches don't happen on every file, however. So far about 40% of my pre-Leopard songs display them. Of course, that's unacceptable, and I'm back to Tiger until Logic Pro 8 on Leopard is finally ready for audio production prime time. That time is, sadly, not yet - at least not on my setup.

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I know what you mean and I've seen/I see it happening with my system. I'm still on 10.4.11 but its similar (perhpas slightly less cpu requirments -but I can't comment on that)


Its understandable that Logic needs more cpu to play a soft instr. "live", as opposed to via recorded midi. Logic can pre-process the prerecorded stuff but it has to be more alert when in record mode and so needs more power (if that makes sense!)


I think the problem comes from the fact logic doesn't release its "alertness" when you de-activate the record mode. It sort of needs a push to stop being so CPU hungry. The fix you suggest certainly works. You could also use a standard midi track or even an audio track (as far as I recall). I think you ight find just stopping and starting playback does it too.


Yes its a bug - along with countless others, sigh.


There is a further point here though that many folk (like Homina) are seeing cpu spikes, that cause all sorts of problems, but this is a different issue to your observations. Perhaps they are related in some way but their problem (in leo/logic8) wont go with your fix.


Thats my take on things anyway.

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